Plot and structure have always been just out of my reach, as well. However, I was looking through a few books to try and get a handle on how I should go about outlining, and I came across a good explaination for plot.
The author said that our problem in plotting lies in the fact that the concept of Plot is often misunderstood. He said to think of it like this: Story is what happened. "John and Mary got a divorce, and then John died in a car accident." Plot injects the causality, why the events happened. "John and Mary got a divorce because Mary had been cheating on John. And then John died in a car accident because he was overcome by grief and the tears blurred his vision, and he ran off the road."
It was a very simple concept, and it really helped to uderstand the relationship and the difference between Plot and Story, and I am now going to start outlining things...which I have never done.
But, at the Overland Park, MO signing a few nights ago, I asked Jim Butcher if he did a lot of outlining before he started writing a book, and he stressed that outlining is essential for well structured and efficient writing. And of course I've heard that before, but you know, it has a certain impact when it comes from Jim Butcher's own mouth in response to one of my questions.
I picked up a book yesterday called "Story Structure Architect" by Victoria Schmidt. So far it's really helping me get a grasp on structuring my story and outlining before I start writing.